Continuously operating kneading and mixing screw device for kneading and mixing kneadable and mixable materials

ABSTRACT

There is disclosed a continuously operating kneading and mixing screw device for kneading and mixing kneadable and mixable materials. This device comprises a power driven shaft mounting interrupted flights and journaled in a housing. Mixing elements extend from the inside of the housing into spaces between the flights. These elements are rotatable and can be turned into selected positions independently of the rotation of the screw shaft.

Unite States Patet Bausch et al.

1451 Mar. 11, 1975 CONTINUOUSLY OPERATING KNEADING AND MIXING SCREW DEVICE FOR KNEADING AND MIXING KNEADABLE AND MIXABLE MATERIALS Inventors: Giinther Bausch, Vaihingen/Enz;

Christian Millauer, Stuttgart; Harald Paul, Kornwestheim, all of Germany Assignee: Werner & Pfleiderer,

Stuttgart-Feuerbach, Germany Filed: Sept. 4, 1973 Appl. No.: 393,838

Foreign Application Priority Data Sept. l, 1972 Germany 2243039 US. CI. 259/191 Int. CI B29b 1/06 Field Of Search 259/191, 192,193, 6, 21,

[56] References Cited UNITED STATES PATENTS 3,804,382 4/1974 Pultz i. 259/[92 FOREIGN PATENTS OR APPLICATIONS 1,245,584 7/1967 Germany 259/191 Primary, Examiner-Robert W. Jenkins Attorne Agent, or FirmHane. Baxley & Spiecens [57] ABSTRACT 7 Claims, 12 Drawing Figures SHL'EI 2 UP 7 MNJ NQE

CONTINUOUSLY OPERATING KNEADING AND MIXING SCREW DEVICE FOR KNEADING AND MIXING KNEADABLE AND MIXABLE MATERIALS The invention relates to a continuously operating kneading and mixing device, and particularly to a kneading and mixing device of the type including a power driven shaft rotatably mounted in a housing and mounting interrupted screw flights and mixing elements extending from the wall of the housing into the spaces defined by the interruption of the screw flights.

BACKGROUND Continually operating kneading and mixing screw devices of the general kind above referred to are widely used for processing soft plastics, such as elastic, pulverized and liquid materials. They are employed, for instance, in the synthetic plastic industry and the rubber industry; they are also employed in connection with the manufacture of electrodes, preparation of molding sand and in connection with the manufacture of various food products.

Various kinds of kneading and mixing devices are already known. There are available for instance, kneading and mixing devices which comprise a rotating and simultaneously axially reciprocating screw which consists of screw flights of screw segments mounted spaced apart on a drive shaft. Devices of this type are disclosed in published German Pat. application No. 1,241,417 and U.S. Pat. No. 3,458,894. Devices of this type further comprise tooth-like kneading members mounted in the housing for the screw for coaction with the interrupted screw flights so that with each revolution of the screw the kneading members enter into interruptions between the flights whereby portions of the material to be treated are pushed into the adjacent screw thread.

The disadvantage of screw devices of this type is that the optimum of the kneading and mixing action cannot be achieved in each case as in actual practice only the rotational speed of the drive of the device can be changed when and while the device is operating. Obviously, such changein the rotational speed of the drive affects the output of the device, but it does not permit adjustment of the mixing elements to the specific properties of the material to be processed. Such an adjustment can be effected only when the device is stopped, and such stoppage entails a loss of working time as generally a rather complex resetting of the device is required.

THE INVENTION It is a broad object of the invention to provide a novel and improved kneading and mixing screw device of the general kind referred to which permits adjustment of the kneading and mixing action of the device in accordance with the specific properties of the materials to be processed when and while the device is in operation.

A more specific object of the invention is to provide a novel and improved kneading and mixing device of the general kind above referred to which is highly reliable and permits adjustment of the mixing intensity within a wide range and without causing substantial changes in the output of the device.

SUMMARY OF THE INVENTION The aforepointed out objects, features and advantages, and other objects, features and advantages which will be pointed outhereinafter, are obtained by rotatably mounting the kneading and mixing elements of the device and providing for the same an adjustable drive which is independent of the drive for the screw shaft.

The invention further provides that several kneading or mixing elements are disposed within the housing of the device in a common plane normal to the axis of the screw shaft and arranged to be jointly adjusted by a common adjustable drive. Such an arrangement greatly facilitates adaptation of the device to specific operating conditions.

In the event the device is designed for large outputs, the adjustment of the elements of such devices is simplified and thus made less expensive by providing several groups of elements in axially spaced planes normal to the axis of the screw shaft and controllable by adjustment of a common drive for the elements in all the groups.

The device according to the invention also provides a simple and highly efficient control of the power input necessary to effect mixing. For this purpose, the kneading and mixing elements are in the form of annular segments which are tapered towards the axis of the screw shaft and have at their ends facing this shaft a concavely and spherically curved surface. This surface coacts with a eonvexly and spherically curved outer surface on the portion of the screw shaft which faces the elements.

A very high flow-throttling or resistance effect can be obtained according to the invention by parallel arrangement of all the kneading and mixing elements disposed in a common plane. More specifically, the elements are so arranged that they can be jointly turned through into a position of maximal through-flow resistance or into a position of minimal flow resistance.

A particularly intimate mixing action can be obtained by providing a rotary drive for the mixing and kneading elements. To obtain such very intimate mixing action without unreasonably increasing the costs involved, the invention also provides that several kneading and mixing elements are disposed circumferentially spaced in a plane normal to the axis of the screw shaft and turnable by a rotary drive common to all the elements in said plane.

To sum up, the advantages obtained with a device according to the invention reside, among others, in that .the mixing action is very considerably increased by simple and inexpensive means and simultaneously the operational reliability of the device is improved. Moreover, by the possibility of changing the mixing action very accurately and continually, automated control of the mixing operation can be readily designed. Furthermore, the dwell time of the different materials to be mixed within the device can be changed within wide limits without unfavorably affecting the output of the device or downgrading the mixing operation.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, several preferred embodiments of the invention are shown by way of illustration and not by way of limitation.

In the Drawings FIG. 1 is a diagrammatic plan view of a screw-type kneading and mixing device according to the invention;

FIG. 2 is a fragmentary longitudinal section of the device according to FIG. 1, the left-hand mixing elements being turned through 90;

FIG. 3 is a section taken on line IIIIII of the device according to FIG. 2;

FIG. 4 is a section taken on line IV-IV of the device of FIG. 2;

FIGS. 5A-5D show several exemplifications of mixing elements as seen in the direction of arrow V in FIG.

FIG. 6 is a fragmentary longitudinal section ofa modification of a screw-type kneading and mixing device according to the invention;

FIG. 7 is a section taken on line VII-VII of the device according to FIG. 6;

FIG. 8 is a section taken on line VIIIVIII of the device according to FIG. 6; and

FIG. 9 is a plan development of a screw with different types of mixing elements for use with the device according to FIG. 6.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the figures in detail, the screw-type kneading and mixing device as shown in FIG. 1 comprises a housing 1 which is composed of suitably joined sections Ia-le. Section 1e mounts a funnel or hopper 2 for feeding the material to be treated into the housing. As can be seen in the plan view of FIG. 1, the operating of hopper 2 displays part of a screw or mixing shaft 4 mounting screw turns or flights 3. Housing sections lb and Id accommodate kneading and mixing elements 5, only shaft 5a being visible in the figure. The shaft is coupled to one end ofa link 6, the other end of which mounts pin 7 engaging an elongate slot 8 ofa setting ring 9 as can best be seen in FIG. 2. As there are two sets of mixing elements 5, two such rings 9 are provided.

The rings are coupled via rods 10 to a suitable common setting device which is shown by way of example as comprising hydraulic cylinders 12 in which pistons 13 mounted on rods 10 are displaceable in either direction. Various other types of conventional setting devices can, of course, be uses and if frequent setting of the mixing elements is not operationally required, adjustment can be manually effected, e.g., by a hand wheel.

Housing section 10 which is in the middle of the housing, includes a degassing port 14. The housing section la which includes the discharge end of mixing shaft 4,

mounts a head member 15 supporting an extrusion die- 16 (FIG. 2) through which is discharged the material as it is pressed out in the form of strands with a selected profile.

The mixing shaft and the mixing elements are more clearly shown in FIG. 2. According to this figure, the screw turns or flights 3 on the mixing shaft 4 in the exemplification a three-gang or triple-threaded screw is shown are interrupted within the mixing zone 17 by mixing elements 5 extending into this zone. The mixing shaft 4 mounts in zone 17 circumferential protrusions 18 with convexly spherically curved outer surfaces. The effective part of the mixing elements 5 has the shape of an annular segment with a cross-sectional outline which is tapered or wedge-shaped towards the axis of the screw shaft. The inner surface of the segment is concavely spherically curved (See FIGS. 5A5D) and thus defines in conjunction with protrusion 18 a gap which is practically of equal width in each angular position of the mixing elements. The mixing elements are joined to their shaft 5a by a generally disc-shaped flange 5b to avoid dead corners, i.e., space areas in which there is very little or even no conveyance of material. Shaft 5a is journalled in a bearing sleeve I9 which is screwed into housing section 117. The bearing sleeve is sealed by a bushing 20 with sealing rings or other sealing means 21. A sealing ring 22 prevents leakage of the material between bearing sleeve 19 and a bore in the housing in which this sleeve is received. Flights 23 of low pitch and low depth at the right-hand end of mixing shaft 4, which as stated before is a triplethreaded screw, by way of example, seal off the passage opening for a drive shaft end 24a of a drive motor (not shown) against leaking or seeping out of material.

The other reference numerals used in FIG. 2 designate the same components as corresponding reference numerals in FIG. 1.

All mixing elements 5 which are disposed in one plane normal to the axis of the mixing shaft are jointly driven via the setting rings 9, or retained in their angular position. The mixing elements are normally parallel one to another and offer minimal flow resistance for material to be processed in the positions shown in FIG. 2 at the left and in the position shown in FIG. 3. While in the positions shown in FIG. 2 on the right side and in FIG. 4 the mixing elements offer maximal throttling. By suitably selecting the configuration of the mixing elements, (see FIGS. 5A-5D) the flow of material can be completely stopped in the last referred-to-position. Depending upon the setting of setting rings 9 with respect to rods 10 (the rods are not shown in FIG. 2), the mixing elements are parallel in plane III-III to those in plane IVIV or normal to those in plane IV-IV or in any selected angular position intermediate the right angle position and the parallel position.

The reference numerals used in FIGS. 3 and 4 have the afore-indicated significance.

Additionally, there is shown in shaft 4 a central bore 24b through which a liquid or gaseous temperature controlling medium can be circulated. Fastening means such as tensioned anchor or screw bolts 25 hold together the housing and intermediate sections 1a le.

FIGS. 5A-5D show various embodiments of kneading and elements 5 as seen from the lengthwise axis of the elements, i.e., in the direction of arrow V in FIG. 4. There is shown in disc-shaped flange or protrusion 5b a concave ball-shaped inner surface 5c and intermediate flanges or protrusions 5d and 5e.

The drive for the mixing device according to FIGS. 1 to 5 via the rods and a hydraulic cylinder is particularly suitable for more or less periodic reciprocating setting of the mixing elements. If required, the mixing elements can also be locked in a selected position. Such adjustable drive constitutes a convenient basis for providing automatic control of the mixing operation.

The mixing device as shown in FIG. 6 is suitable for automatic control of the mixing operation but it is preferably used when a particularly intensive mixing and kneading action are desired. Similar to the arrangement in FIGS. 2 to 4, kneading and mixing elements 5' which are rotatably mounted in intermediate housing section lb, are set by means of a rotary drive which is independent of the drive for shaft 4. Three elements are mounted in the housing in a plane VII-VII which is normal to the axis of the mixing shaft at equal angular spacing (See also FIG. 7). The shafts 5a for the mixing elements mount conical toothed sectors 26 which are jointly driven by a large level gear 27 which is journalled by means of a suitable bearing 28 such as a sliding bearing on housing section 1b. Bevel gear 27, in addition to its inner teeth, has outer teeth by means of which it is driven via a pinion 29 by an electric motor 30 mounted on housing section 1c.

For some of the mixing elements journalled in the housing, a rotary drive is particularly suitable as shown in the plane VIllVIll of FIG. 6 and in FIG. 8. The shaft is driven via a coupling 31 by an electric motor 32 which, in turn, is mounted via a bracket 33 and a spacer 34 on housing section 1d. Other reference numerals used in FIGS. 6 to 8 have the same significance as previously described but are primed to indicate modifications.

FIG. 9 shows a development of part of a screw or mixing shaft with flights 3 and screw threads 4b. In connection therewith, there are shown several embodiments of elements 5 for use with mixing device according to FIGS. 6 to 8. There is also shown a projection of the active part of elements at a right angle to the axis of the mixing shaft. As is apparent, the strands of material as they are forced out of screw threads 4g are gripped by the kneading and mixing elements, sections, reversed and partly twisted whereby a very intensive mixing action is obtained.

Such mixing action is also obtained when the mixing elements are held in a fixed position and, or course, it is also affected by the shape of the elements and the angular positions thereof. With rotating mixing elements, the mixing action depends largely on the rotational speed of the mixing elements. The elements as shown at 9.1, 9.5, 9.6 and 9.7 are particularly suitable for a rotary drive. As it is evident, the magnitude of the volume of material as gripped by the mixing elements does not only depend on the afore-referred to parameters but also on the rotational speed and the number of flight threads on the screw shaft.

The advantages which are obtained by the invention, i.e., a sensitive control of the mixing operation, are also obtained with mixing devices with twin or more screws.

While the invention has been described in detail with respect to certain now preferred examples and embodiments of the invention, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended, therefore, tocover all such changes and modifications in the appended claims.

What is claimed is:

l. A continuously operating kneading and mixing screw device for kneading and mixing kneadable and mixable materials, said device comprising in combination:

a housing;

a power driven shaft rotatably mounted in said housing and mounting screw flights, said flights being interrupted to define spaces therebetween; kneading and mixing elements extending from the inside of the housing into said spaces between the 5 flights, said elements being disposed in circumferentially spaced relationship and arranged in groups, each of said groups being located in a plane normal to the center axis of said shaft;

mounting means rotatably supporting said mixing elements; and

drive means coacting with said elements for turning the same independently of rotation of said shaft, said drive means being coupled to the elements in said groups for joined turning of the elements, said drive means being adjustable for controlling the angular positions of the elements in said groups.

2. The screw device according to claim 1 wherein said elements are inwardly tapered toward said shaft, a wall portion of the elements facing the shaft having a concavely and circularly curved configuration relative the shaft and the portions of the shaft facing said curved wall portions having a convexly and circularly curved configuration.

3. The screw device according to claim 1 wherein all the elements in a group are disposed in mutually parallel relationship in the respective plane, said adjustable drive means being settable for selectively turning the elements in each group between a position of maximal flow resistance to material conveyed by screw flights on the shaft and a position of minimal flow resistance to said conveyance.

4. The screw device accordinng to claim 3 wherein said drive means for the elements is rotatable.

5. The screw device according to claim 4 wherein at least two of said elements are arranged in a group in circumferentially spaced relationship and disposed in a common plane normal to the center axis of the shaft, said drive means being coupled to said elements for jointly turning the same into selected angular positions.

6. The screw device according to claim 1 wherein said drive means comprises a setting ring encompassing and turnable about the outside of said housing and linking means coupling said ring with said elements, turning of said ring causing a corresponding turning of the elements coupled to said ring.

7. The screw device according to claim 6 wherein said elements are arranged in groups and are disposed in each group in mutally parallel relationship in a plane normal to the center axis of said shaft, the elements in each group coupled to said ring via said linking means for selectively turning the elements between a position of maximal flow resistance to material conveyed by screw flights and a position of minimal flow resistance to such conveyance. 

1. A continuously operating kneading and mixing screw device for kneading and mixing kneadable and mixable materials, said device comprising in combination: a housing; a power driven shaft rotatably mounted in said housing and mounting screw flights, said flights being interrupted to define spaces therebetween; kneading and mixing elements extending from the inside of the housing into said spaces between the flights, said elements being disposed in circumferentially spaced relationship and arranged in groups, each of said groups being located in a plane normal to the center axis of said shaft; mounting means rotatably supporting said mixing elements; and drive means coacting with said elements for turning the same independently of rotation of said shaft, said drive means being coupled to the elements in said groups for joined turning of the elements, said drive means being adjustable for controlling the angular positions of the elements in said groups.
 1. A continuously operating kneading and mixing screw device for kneading and mixing kneadable and mixable materials, said device comprising in combination: a housing; a power driven shaft rotatably mounted in said housing and mounting screw flights, said flights being interrupted to define spaces therebetween; kneading and mixing elements extending from the inside of the housing into said spaces between the flights, said elements being disposed in circumferentially spaced relationship and arranged in groups, each of said groups being located in a plane normal to the center axis of said shaft; mounting means rotatably supporting said mixing elements; and drive means coacting with said elements for turning the same independently of rotation of said shaft, said drive means being coupled to the elements in said groups for joined turning of the elements, said drive means being adjustable for controlling the angular positions of the elements in said groups.
 2. The screw device according to claim 1 wherein said elements are inwardly tapered toward said shaft, a wall portion of the elements facing the shaft having a concavely and circularly curved configuration relative the shaft and the portions of the shaft facing said curved wall portions having a convexly and circularly curved configuration.
 3. The screw device according to claim 1 wherein all the elements in a group are disposed in mutually parallel relationship in the respective plane, said adjustable drive means being settable for selectively turning the elements in each group between a position of maximal flow resistance to material conveyed by screw flights on the shaft and a position of minimal flow resistance to said conveyance.
 4. The screw device accordinng to claim 3 wherein said drive means for the elements is rotatable.
 5. The screw device according to claim 4 wherein at least two of said elements are arranged in a group in circumferentially spaced relationship and disposed in a common plane normal to the center axis of the shaft, said drive means being coupled to said elements for jointly turning the same into selected angular positions.
 6. The screw device according to claim 1 wherein said drive means comprises a setting ring encompassing and turnable about the outside of said housing and linking means coupling said ring with said elements, turning of said ring causing a corresponding turning of the elements coupled to said ring. 